Hydrogen Enriched Natural Gas Research Articles

Experimental study on hydrogen-enriched natural gas jet fire hazards: Assessment of the flame geometrical parameters

In the future, hydrogen will be more frequently injected into natural gas networks for storage and transportation purposes. A diffusion jet flame forms when gaseous fuel leakage occurs during the transportation or utilization of hydrogen-enriched natural gas, and the fuel is ignited by an ignition source in still air. In the study, methane was chosen to simulate natural gas. Experiments with the hydrogen addition fraction reaching up to 20% were performed to study the effects of the initial flame angle (θ = 90°, 60°, 30°, 0°, and −30°), variable nozzle diameter (de = 3.15, 4, 4.94, 5.65, and 6 mm) and a multitude of fuel flow rates (10, 20, 30, 40, 50, and 60 L/min) on the morphological parameters of the gas jet flames. The geometrical features of the jet flame were determined via video processing for each experiment. The geometrical parameters of hydrogen-enriched natural gas were quantified under different conditions. The experimental results indicate that a dimensionless prediction model was established for the flame height of hydrogen-enriched natural gas by modifying the flame Froude number (Frf) for vertical jet flames. For upward jet flames, the normalized flame horizontal projection length (Lx) of hydrogen-enriched natural gas is well correlated with Q∗. A global prediction model for inclination angles of 0° ≤ θ ≤ 60° and 2000 < Q∗<20,000 was proposed based on the experimental data. For downward jet flames, the normalized horizontal projection length and downward extension length (Ld) of the hydrogen-enriched natural gas jet flame are correlated with Q∗, with powers of 2/5 and 3/5, respectively. Dimensionless prediction models for the horizontal projection length and downward extension length are given by modifying the flame Froude number. Quantitative results were proposed in order to gain insight into the development of the key parameters and the effects on the environment, from which extinguishing concepts and safety areas can be directly derived.

CO2 effect on the fatigue crack growth of X80 pipeline steel in hydrogen-enriched natural gas: Experiment vs DFT

Utilizing the existing natural gas grid presents a promising method for transporting hydrogen on a large scale. However, the effects of natural gas and its impurities on hydrogen-assisted cracking in pipeline steel have not been adequately studied. This study aims to investigate the fatigue performance of X80 pipeline steel in hydrogen-enriched natural gas (HENG) environments and in mixtures containing the impurity CO2. This is achieved through fatigue crack growth rate (FCGR) tests and density functional theory (DFT) calculations. The experimental results show that the FCGR in H2 is slightly faster than that in HENG, whereas it is slower than that in the N2/CO2/H2 mixtures. The enhanced FCGR by CO2 further increases with the increasing CO2 content. DFT computational results indicate that the adsorbed CO2 on the iron surface significantly accelerates the migration of H atoms from surface to subsurface. This promotes the entry of hydrogen into the steel.

Numerical simulation on combustion characteristics of methane/hydrogen blended fuel for non-premixed conical bluff body burner

Blending hydrogen into methane impacts flame stability, morphology, and pollutant emissions. This study, set against the backdrop of hydrogen-enriched natural gas combustion technology, employs a non-premixed coaxial burner with conical bluff body to create recirculation zones for flame stabilization. Combining EDC and GRI-Mech 3.0, the research fills in the gap of effects of hydrogen blending ratio (0–100%) and equivalence ratio vary (0.4–1.4) within a wide range. Keeping equivalence ratio and fuel volume flow rate as constants, as increasing hydrogen blending ratio, the mean velocity in the chamber decreases, the size of vortex structure located in outer recirculation zones reduces, and the flame length is shortened, illustrating the reaction zone shifts to chamber inlet. Furthermore, when Ф = 1.4, average temperature and temperature uniformity are averagely larger 59.82% and 4.21% than that under Ф = 0.4. The CO2 emission at XH2 = 80% is 54.70% averagely lower than that at XH2 = 0%, but peak concentration of NO increases.

Thermodynamic and environmental analyses of a hydrogen-enriched natural gas oxy-fuel combustion power plant

Hydrogen-enriched natural gas is regarded as a promising low-carbon fuel in clean energy field. A hydrogen-enriched natural gas oxy-fuel combustion power plant is established to study the effect of hydrogen content on system thermodynamic performance. Three different diluents including recycled flue gas (RFG), H2O, and CO2 are used to moderate the high combustion temperature. The transcritical CO2 cycle is adopted to efficiently utilize flue gas waste heat. As the hydrogen blending ratio increases from 0 to 0.5, the efficiency of the O2/RFG system, O2/H2O system and O2/CO2 system increases by 1.45%, 1.13% and 1.16%, respectively. The RFG system is preferable to realize high efficiency that can reach 50.23%. In the proposed systems, the carbon capture rate (CCR) decreases while specific CO2 emission (SECO2) increases with the hydrogen addition. In O2/RFG system, the CCR reaches a minimum of 99.09% when SECO2 is 3.81. The study results can have a positive influence on the utilization of hydrogen energy.

Experimental investigation of hydrogen enriched natural gas combustion with a focus on nitrogen oxide formation on a semi-industrial scale

Combustion of hydrogen-enriched natural gas is a valuable short-term strategy for reducing CO2 emissions from high temperature industrial heating. This paper presents several experiments on combustion characteristics and the formation of nitrogen oxides. The experiments included hydrogen contents up to 100% and fuel heat inputs up to 75 kW. Water-cooled lances were used to influence the furnace temperature. The analysis includes the distribution of furnace temperatures, the composition of flue gas, the cooling capacity of the lances under steady-state operating conditions, and OH*-chemiluminescence imaging of the near burner region. The presented results demonstrate the dependence of furnace conditions and NOX formation on various factors, such as different air inlet fluxes, furnace temperature, and fuel composition, for constant heat inputs. Efficiency increased by up to 5.5% and significant changes in flame shaped along with a maximum increase in NOX emissions when comparing natural gas to hydrogen was measured at 167%.

Numerical investigation on knock intensity, combustion, and emissions of a heavy-duty natural gas engine with different hydrogen mixing strategies

With the continuous development of hydrogen energy technology, mixing hydrogen has become a potential method to enhance the performance of natural gas engines and reduce emissions. Aiming to offer guidance for optimizing strategies for mixing hydrogen from the perspectives of knock control and thermal efficiency enhancement, a three-dimensional model of a commercial heavy-duty natural gas engine is constructed based on the actual boundary conditions from a high load bench test. In this study, simulations were conducted under conditions where the hydrogen volume fraction ranged from 0% to 40%. The study explored the effects of two injection strategies, port fuel injection of hydrogen-enriched natural gas (PFI) and port fuel injection of natural gas combined with direct injection of hydrogen into the cylinder (PFI + DI), on engine knocking, performance, and emissions. Results indicate that for various injection strategies, there is an increasing trend in knock intensity (KI) with the higher hydrogen mixing ratio. When the hydrogen volume fraction exceeds 20%, the timing of direct hydrogen injection significantly affects KI. This effect is mainly caused by the distribution of unburned hydrogen at the knock onset crank angle (KOCA). Compared to other injection strategies, the PFI + DI strategy when the direct hydrogen injection time at 120°CA BTDC results in a high concentration of hydrogen near the spark plug at the ignition moment, combined with good mixture uniformity in the cylinder. This leads to the shortest CA0-10 and CA10-90, and achieves a maximum indicated thermal efficiency (ITE) of 44.68% under 20% hydrogen volume fraction. Compared to the original natural gas engine, the ITE increased by 2.9% and the NOx emissions increased by 166%, while the HC and CO emissions decreased by 88% and 53%.

Comparative Study of Mathematical Models for Describing the Distribution of Hydrogen-Enriched Natural Gas in Enclosed Spaces

Comparative Study of Mathematical Models for Describing the Distribution of Hydrogen-Enriched Natural Gas in Enclosed Spaces

Low carbon economic scheduling model for a park integrated energy system considering integrated demand response, ladder-type carbon trading and fine utilization of hydrogen

With the intensification of energy crisis and the aggravation of greenhouse effect, It is particularly essential to develop a sustainable energy system. For this reason, a low-carbon economic dispatch model for a park integrated energy system considering integrated demand response and ladder-type carbon trading is designed. First, a refined model of hydrogen utilization is developed, and hydrogen-enriched natural gas as hybrid energy to extend the scenario of hydrogen utilization. Second, in order to investigate the effect of demand response mechanism and carbon trading mechanism on the system, an integrated demand response model for electricity-heat-gas load and a ladder-type carbon trading model that takes into account the carbon emissions of the whole process are constructed respectively. Finally, based on above models, a low-carbon economic scheduling model is established to optimize the total cost of the system. The simulation results show that the refined modeling and hydrogen-doped operation of the equipment can help reduce the system's carbon emissions. When the integrated demand response mechanism and the ladder-type carbon trading mechanism are considered together, the carbon emissions of the system are greatly reduced, while its total cost can be kept low.

Thermodynamic and emission characteristics of a hydrogen-enriched natural gas-fired boiler integrated with external flue gas recirculation and waste heat recovery

Hydrogen-enriched natural gas (HENG) is a low-carbon fuel and its utilization in combustion devices has been under extensive discussion recently as it is a promising way to reduce the CO2 emission during combustion. The applicability of HENG in the existing natural gas-fired combustion equipment in terms of its efficiency and emissions attracts increasing attention, especially for industrial and domestic small-scale boilers. In this study, the thermal efficiency and pollutant emissions of a 4.2 MWth HENG-fired boiler integrated with external flue gas recirculation (FGR) were respectively evaluated based on the thermodynamic and heat transfer models and the Chemical Reaction Network model. Results suggested that NOx emission rose by ∼19% as the hydrogen volumetric fraction in the fuel increased from 0 to 0.4 at a constant excess air ratio and FGR rate. To suppress the NOx rise, the FGR rate was tuned higher while the system thermal efficiency decreased subsequently. To further improve the overall system thermal efficiency, a cascade flue gas waste heat recovery strategy including sensible heat recovery using an external economizer and latent heat recovery using dual-spray heat exchangers was proposed. The thermodynamic analysis demonstrated that the external economizer improved the overall system thermal efficiency by 0.4% - 0.7% and the dual-spray heat exchangers promoted the overall system thermal efficiency by over 5%. Thus, a comprehensive performance optimization strategy was developed for HENG-fired boilers in terms of their overall system thermal efficiency promotion, NOx emission control, and CO2 emission reduction.

Hydrogen volumetric fraction effects on HCNG refuelling station CAPEX

Greening the transport sector is crucial for the achievement of the ambitious decarbonisation goals set by the Conference of the Parties (COP21) Paris agreement to keep global warming “well below 2 degrees Celsius above preindustrial levels, and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius”. Battery electric vehicles and hydrogen fuel cell electric vehicles will play a key role in the reduction of greenhouse gas emissions in the road mobility. Nonetheless, those technologies still need to face some technological challenges. Hence, hydrogen enriched natural gas (HCNG) can play an important role as bridging technology. This study envisages the upgrade of an existing compressed natural gas (CNG) refuelling station (RS) in HCNG-RS. Particularly, an analysis regarding the impact of different hydrogen volumetric fractions in the blend on the total CAPEX of the HCNG refuelling station is carried out, by evaluating the HCNG fill-up demands for a proper refuelling station sizing. The proposed HCNG refuelling station layout foresee the on-site hydrogen production by means of an electrolyser fed by PV energy. Each component of the station has been adequately sized based on the resulting peak HCNG refuelling demand. The highest CAPEX value is recorded for the 30%vol. HCNG, amounting up to 3.52 M€.

Effect of hydrogen-enriched natural gas on flue gas waste heat recovery potential and condensing heat exchanger performance

Hydrogen-enriched natural gas (HENG) is one of the significant ways to store, transport, and utilize hydrogen energy. This paper presents the characteristics of HENG and flue gas, energy saving, carbon reduction, and condensate recovery potential of flue gas waste heat. Based on the theoretical and experimental study of the existing flue gas condensing heat exchanger (FGCHE) added at the rail of gas-fired boiler, the performance of the FGCHE under different hydrogen blending ratios is studied. The results show that augmenting the hydrogen blending ratio decreases the volume heating value of HENG, and CO2 content of flue gas. Meanwhile, the mass heating value of the HENG, the water vapor content, and dew point temperature of flue gas increase as the hydrogen blending ratio increases. The flue gas waste heat recovery utilization ratio and energy-saving efficiency of the FGCHE can be promoted. Moreover, the heat transfer capacity of the FGCHE using HENG is enhanced, while the flue gas flow pressure drop is reduced. Compared with the FGCHE used in pure natural gas systems, the all-hydrogen system increases the flue gas waste heat recovery amount by 62.4–120.4 %, reduces the flue gas flow pressure drop by 33.9 %, and reduces the carbon emission by 100 %.

Hydrogen Combustion: Features and Barriers to Its Exploitation in the Energy Transition

The aim of this article is to review hydrogen combustion applications within the energy transition framework. Hydrogen blends are also included, from the well-known hydrogen enriched natural gas (HENG) to the hydrogen and ammonia blends whose chemical kinetics is still not clearly defined. Hydrogen and hydrogen blends combustion characteristics will be firstly summarized in terms of standard properties like the laminar flame speed and the adiabatic flame temperature, but also evidencing the critical role of hydrogen preferential diffusion in burning rate enhancement and the drastic reduction in radiative emission with respect to natural gas flames. Then, combustion applications in both thermo-electric power generation (based on internal combustion engines, i.e., gas turbines and piston engines) and hard-to-abate industry (requiring high-temperature kilns and furnaces) sectors will be considered, highlighting the main issues due to hydrogen addition related to safety, pollutant emissions, and potentially negative effects on industrial products (e.g., glass, cement and ceramic).

Numerical Simulation and Performance Evaluation of Hydrogen-Enriched Natural Gas for an Industrial Burner in a Testing Chamber

A two-step numerical concept was developed for modelling combustion and predicting nitrogen oxide emissions. The model was validated by the Sandia flame D experiment and with measurement data from burners on industrial furnaces. In this paper, the developed model was implemented to evaluate the influence of hydrogen blending with natural gas up to 40 vol.% on an industrial burner with oxidizer temperatures at 300 K and 813 K to assess the performance of the burner without altering the power output of the burner. An experimental test facility is under construction, and the feasibility of using this industrial burner on the test facility with different fuel mixtures was analyzed. Temperature, flow field, and emission characteristics were investigated. Using 40 vol.% hydrogen with natural gas resulted in a decrease of 14.82% in CO2 emissions and an increase of in 16.1% NO emissions when combusted with air at 300 K. The temperature profile indicated that the burner produces a symmetrical flame profile with preheated air and an asymmetrical flame profile with ambient air.

Experimental investigation of the combustion characteristics in oxy-fuel combustion of hydrogen-enriched natural gas on a semi-industrial scale

The present paper deals with the influence of different hydrogen enrichment on oxy-fuel combustion of natural gas, enabling important insights regarding decarbonization of high-temperature processes. Experiments were conducted using a high-impulse multifuel burner for industrial applications for hydrogen contents between 0 and 100%. The fuel input varied between 100 and 140 kW, while water-cooled lances were used to simulatethermal loads. The analysis included temperature measurement points, atomic and energy balances and the cooling capacity of the thermal load for steady-state operation. The obtained results show that the flue gas temperature decreases by up to 126 K for pure hydrogen, while the cooling capacities of the thermal load increased by up to 16.3% at constant calorific energy input. The flames for different hydrogen enrichments were also compared visually. Overall, all investigated fuel blends were highly interchangeable with the investigated burner and showed high potential for a timely decarbonization of industrial heating.

Modeling the emission characteristics of the hydrogen-enriched natural gas engines by multi-output least-squares support vector regression: Comprehensive statistical and operating analyses

Modeling the emission characteristics of the hydrogen-enriched natural gas engines by multi-output least-squares support vector regression: Comprehensive statistical and operating analyses

Comprehensive Review on Thermal Performance Enhancement of Domestic Gas Stoves.

Cooking is a daily activity in every household, which consumes energy and produces pollution. Using clean gas fuels instead of traditional solid fuels will significantly reduce household air pollution. Although the use of clean-burning burners can reduce emissions, early domestic gas cookers had poor thermal performance. Currently, even small improvements in efficiency can result in significant energy savings due to the large number of domestic gas stoves in use. There has been a long history of research into the development of domestic gas stoves to improve performance and reduce energy consumption. Meanwhile, research into the use of hydrogen-enriched natural gas as a promising environmentally friendly fuel is increasing. In this paper, we perform a descriptive statistics and graphical visualization of network analysis by combining common databases with Bibliometrix. We also analyze the energy balance of domestic gas stoves and the influence of a single factor and multiple factors on stove performance. Then we provide a detailed overview of some research technologies in enhancing the thermal performance of gas stoves. We also discuss the research progress and application prospects for the use of hydrogen-enriched natural gas as a fuel in domestic gas stoves and identify areas for future research and issues that need attention.

Novel approach for efficient operation and reduced harmful emissions on a dual-fuel research engine propelled with hydrogen-enriched natural gas and diesel

ABSTRACT The stricter emission norms have created a need to study recent combustion technology in internal combustion engines. Dual-fuel (DF) combustion technology is one of the key techniques to achieve future emission goals. Natural gas is one of the easily available low-reactive fuels worldwide that can be used in the DF combustion strategy. The main problem with using NG in the DF strategy is its lean-burning ability to produce emissions like HC and CO. The combustion losses associated due to crevice losses in the piston geometry are also the reasons for getting degraded engine performance. In the present study, the lean flammability of NG was improved by enriching it with hydrogen. The combustion losses were reduced using modified disc piston geometry with lower crevice volume. The results showed that the thermal efficiency obtained using HENG/diesel DF strategy with disc piston (DF disc) was only less than 0.3%, 0.4%, and 1% for low, mid, and high load conditions compared to conventional compression ignition mode using bowl piston (CI bowl). The change in piston geometry from bowl to disc type using the DF strategy improved the thermal efficiency by about 3.8%, 3.3%, and 2.7% for three load conditions. The NOx and smoke opacity reduction by about 6% to 19% and 40% to 60% in DF disc mode was achieved compared to CI bowl mode.

CLIMATE AND ENVIRONMENTAL BACKGROUNDS OF FUEL UTILIZATION, INFLUENCING UPON ALTERATION THE EUROPEAN AND UKRAINIAN TRENDS OF GAS SUPPLY P.1 PRESENT REQUIREMENTS TO SELECTION THE GAS FUELS. THERMODYNAMIC EVALUATION THE PRINCIPAL CHARACTERISTICS OF GAS FUEL

The work examines the starting points on the formation of fuel markets in Europe within the framework of the concept of sustainable development of the countries’ economics, taking into account the main limitations, primarily the climatic and environmental consequences of fuels combustion. This approach has led in the past years to simultaneous increase in absolute volumes’ consumption of mineral (organic, carbon-rich) fuel’s flow rate and to reduction of their shares in the overall fuel balance. The relevant changes had occurred because of simultaneous production and consumption the alternative fuels, including renewable gas and energy sources. New schemes, methods and ways of fuel supply have been analyzed, including maritime transportation of liquefied fuels (liquefied natural gas LNG, liquid hydrocarbons LPG, ammonia NH3) along with creation of a modern tanker fleet with floating and land-based regasification and gas storage (FSRU) systems; systems of interconnecting the pipelines for fuel supply, including hydrogen-enriched natural gas (HENG). According to the cultivated opinion, the global warming is considered as a consequence of the carbonization of environment due to emission of C-rich combustion products (CO2) into the atmosphere. The specified contribution of CO2 to atmospheric pollution is caused by the insufficient efficiency of fuel use, for example, in heating furnaces (up to 40 % of the total amount of fuel consumed in the industry is burned in furnaces). If the emissions value of a conventional natural gas combustion systems in furnaces meets the level of emissions up to 0.45 kg СО2/kW.h, then in the case of equipping the furnace with an efficient waste gas heat recovery system, the emissions are reducing to 0.2–0.25 kg СО2/kW.h, (Wunning J.). The determinant role of the efficiency of fuel use ηf has been correlated with the scale of atmospheric pollution with greenhouse gases (CO2) emission by means of thermodynamic analysis of energy efficiency. The efficiency of fuel utilization: by enthalpy ηH and by exergy ηeff — has been computed for the cases of burning the widespread fuels and the comparative analysis has been performed. The calculations of thermal energy characteristics of the fuels have been carried out by using the original author’s methodology based upon assumption of equilibrium thermodynamics for the cases of using the widespread gas fuels within the temperature range T from the standard T0 to the theoretical combustion temperature TT. In accordance with original author’s method the most important heat engineering characteristics of the fuels have been studied by means of approaches of equilibrium thermodynamics. Higher and lower combustion heat, higher and lower Wobbe numbers, theoretical (adiabatic) combustion temperature of the widespread fuels have been determined. An influence of hydrogen content in CH4/H2 gas fuel mixtures on the mentioned properties has been determined. From the list of firing engineering characteristics, the formation of the methane number MN for different organic and alternative fuels have been considered. The accumulated numerical values of MN for the widespread types of fuels have been stated and compared. Bibl. 38, Fig. 4, Tab. 1.

Hydrogen enriched natural gas as fuel for CHP units

This study investigates the potential benefits and drawbacks of adding hydrogen to natural gas grids on stationary cogeneration plants. Fuel blended with up to 30% hydrogen by volume was tested using a commercial six-cylinder spark ignition engine designed for pure natural gas operation without modifications to the engine. In line with normal practice for cogeneration plant engines, the power output, the lower heating value of the air/fuel mixture, the ignition timing and the engine speed were held constant. Results show that increasing hydrogen concentration led to an earlier peak cylinder pressure, indicating significantly accelerated combustion. As a result, peak pressures were up to 39% higher than with natural gas and up to 10% of fuel burned before top dead center. Despite this, thermal efficiency improved up to 6%. Cycle-by-cycle variation decreased by half, indicating reduced misfires on account of hydrogen. However, nitrogen oxide emissions increased exponentially with increasing hydrogen amounts. Our findings suggest that hydrogen-enriched natural gas is a promising fuel for stationary cogeneration plants, but modifications to engine control settings are necessary to ensure optimal performance and compliance with nitrogen oxide emission regulations. These modifications might include adjustments to the mixture control system and ignition timing.

Energy saving analysis and thermal performance evaluation of a hydrogen-enriched natural gas-fired condensing boiler

Hydrogen-enriched natural gas (HENG) has attracted widespread attention due to its lower pollutant emissions and industrial decarbonization in the past decades. HENG combustion boosts the water content in the flue gas, which is highly favorable for condensing boilers to recover additional latent heat. The energy saving and thermal performance of a condensing boiler burning HENG were evaluated at a constant heat load of 2.8 MW in this study. The variations in combustion products and boiler efficiency were investigated based on the material balance and energy conservation. The heat transfer calculations were employed to evaluate the thermal performance of boiler heating surfaces. The energy recovery performance of the condenser was assessed via a thermal design method. Results show that H2 enrichment enhances the radiation intensity of the flame due to the incremental triatomic gases with higher emissivity in the furnace. The heat absorption ratio increases with H2 enrichment in the radiative heating surface, while it shows a reverse tendency in the convective heating surface. The condensing boiler efficiency based on lower heating value increases from 101.83% to 110.60%, the total heat transfer rate of the condenser increases from 2.77 × 105 W to 4.61 × 105 W, and the total area required decreases from 46.45 m2 to 42.16 m2, as the H2 enriches from 0 to 100% under the exhaust flue gas temperature of 318 K. Although the amount of recoverable heat in the exhaust flue gas increases considerably after H2 blending, the original condenser with natural gas as the designed fuel could meet the requirements of the heat recovery for HENG without increasing the extra heating surface. When the H2 fraction is enriched from 0 to 100%, CO2 emission intensity drops from 6.05 × 10−8 kg J−1 to 0. This work may offer some theoretical references for the application and generalization of HENG condensing boilers.